The present invention relates to an indexing tool turret for a machine tool. In particular, the present invention relates to an improved three piece coupling arrangement for a turret indexing mechanism that permits rotation of a tool turret during an indexing operation and prevents rotation of the tool turret during a machining operation. An air bearing is provided to reduce friction between the tool turret and the indexing mechanism during the indexing operation.
Machine tools with indexing tools turrets have found widespread use in the machine tool industry. The indexing tools turrets permit a single machine tool to perform drilling, turning, milling, boring, etc. on a workpiece by selectively indexing the tools located on the tool turret. One such type of indexing tool turret is disclosed in U.S. Provisional Patent Application No. 60/099,295, entitled xe2x80x9cIndexing Tool Turretxe2x80x9d and U.S. patent application Ser. No. 09/389,051, entitled xe2x80x9cIndexing Tool Turret.xe2x80x9d Both applications are assigned to the same assignee as the present application, and are specifically incorporated herein by reference.
A positioning mechanism is needed to selectively index the tool turret to a desired orientation to perform a desired machining operation. Many of the prior art positioning mechanisms are not suitable for high speed indexing and/or high precision indexing. These mechanisms provide for the axial movement of the tool turret during the indexing operation. The tool turrets are quite heavy. The axial movement of these heavy tool turrets during the indexing operation generates an inertia that can adversely impact the precise alignment of the tool turret, which is necessary for today""s high precision products. Furthermore, this axial movement of the tool turret increases the overall indexing time.
There is a need for a positioning mechanism for selectively indexing a tool turret that does not require substantial axial movement of the tool turret. Others have attempted to develop positioning mechanisms for indexing a tool turret with this objective in mind. Indexing mechanisms are disclosed in U.S. Pat. No. 5,271,134 to Schips, entitled xe2x80x9cTool Turret With Axial Reactive Force,xe2x80x9d U.S. Pat. No. 5,632,075 to De Bernardi et al., entitled xe2x80x9cTool-Carrier Turretxe2x80x9d and U.S. Pat. No. 5,657,523 to Lin et al., entitled xe2x80x9cPositioning Mechanism of Turret Index.xe2x80x9d These indexing mechanisms have rather complex constructions. Furthermore, there is contact between the locking mechanism and the tool turret during the indexing operation. The tool turret and the indexing mechanism are further subject to increased torsional resistance and increased friction. Over time, this can result in damage to the tool turret and the indexing mechanism, which leads to increased maintenance costs and increased down time of the machine tool for repair. These devices also lack accurate control of the axial movement of the turret during the machining operation, which can create bending or lifting forces on the turret. These forces can adversely impact the machining of the workpiece.
It is an object of the present invention to provide a three piece coupling arrangement for an indexing mechanism for a machine tool that eliminates the problems identified in the above-identified prior art.
It is another object of the present invention to provide a machine tool having an improved turret indexing mechanism for selectively indexing the tool turret to a desired position so that a live tool or a stationary tool may perform a machining operation on a workpiece.
It is another object of the present invention to provide an improved turret indexing mechanism having a three piece coupling assembly for selectively engaging the tool turret during a machining operation to prevent rotation of tool turret.
It is another object of the present invention to provide an improved turret indexing mechanism having a three piece coupling assembly for selectively disengaging the tool turret to allow the rotation of the tool turret to a desired position during a turret indexing operation.
It is another object of the present invention to provide an assembly that reduces friction between the three piece coupling arrangement and the tool turret during an indexing operation.
It is another object of the present invention to provide a selectively operable bearing assembly that reduces friction between the three piece coupling arrangement and the tool turret during an indexing operation.
It is another object of the present invention to provide a selectively operable bearing assembly that utilizes air to reduce friction between the three piece coupling arrangement and the tool turret during an indexing operation.
It is another object of the present invention is to provide an improved turret indexing mechanism that can accomplish the above-identified objects with a simple and compact construction.
It is another object of the present invention to provide an indexing mechanism for a machine tool that can change live and/or stationary tools at high speed.
The foregoing and other objects, features, characteristics and advantages of the present invention as well as the methods of operation and functions of the related elements of structure, and the combination of parts and economies of manufacture, will be apparent from the following detailed description and the appended claims, taken in connection with the accompanying drawings, all of which form a part of the specification.
In response to the foregoing challenges, applicants have developed an innovative indexing tool turret assembly for a machine tool, whereby the tool turret assembly can be quickly and smoothly indexed to a new location. The indexing tool turret assembly includes a tool turret assembly rotatably supported on the machine tool, and an indexing assembly for selectively rotating the tool turret assembly to a desired location. The indexing assembly includes a locking assembly to prevent rotation of the tool turret assembly during operation of either a stationary tool assembly or live tool assembly located on the tool turret assembly.
In accordance with the present invention, a cushioning bearing assembly is provided for selectively separating the tool turret assembly from the locking mechanism during an indexing operation. The cushioning bearing assembly provides a slight lift to separate the tool turret assembly from the locking mechanism to reduce friction and other potential damaging forces between these components. It is contemplated that the cushioning bearing assembly includes a supply of air that selectively separates the tool turret assembly from the locking assembly.
In accordance with the present invention, the locking assembly includes a rotatable coupling member connected to the tool turret assembly, a fixed coupling member, and a locking mechanism for selectively locking the rotatable coupling member to the fixed coupling member. The rotatable coupling member is selectively rotatable with respect to the fixed coupling member. The locking mechanism locks the rotatable coupling member to the fixed coupling member during a machining operation. It is contemplated that the supply of air of the cushioning bearing assembly is provided to separate the tool turret assembly from the fixed coupling member.
The locking mechanism includes a movable coupling member adapted to selectively engage the fixed coupling member and the rotatable coupling member. The locking mechanism further includes an actuator assembly for selectively moving the movable coupling member into engagement with the fixed and rotatable coupling members.
The present invention is also directed to a method of indexing a rotatable tool turret assembly of a machine tool. The method in accordance with the present invention includes providing an indexing assembly for selectively rotating a tool turret assembly to a desired location. The indexing assembly includes a locking assembly to prevent rotation of the tool turret assembly during the machining operation. The method further includes separating the tool turret assembly from the locking assembly by providing a supply of air to selectively separate the tool turret assembly from the locking assembly. The supply of air forms a cushion of air between the tool turret assembly and the locking assembly. The method further includes rotating the tool turret to the desired location. After rotation, the supply of air is terminated and the locking assembly is operated to prevent rotation of the tool turret assembly.